1. Technical Field
The present invention relates generally to multi-layer sliding bearings of the type having two or more metal layers bonded to a steel backing strip for use in journaling a shaft or the like.
2. Related Art
Sleeve or sliding bearings for use as main bearings or connecting bearings in internal combustion engines can be divided into two main categories. The categories: (1) bimetal bearings, which consist of a steel backing and a lining alloy on the inside diameter; (2) trimetal bearings, which include a third layer which is typically electro deposited over the lining alloy.
Bimetal bearings typically include an aluminum based lining material placed on the inside diameter of a bearing. This type of bearing offers advantages over trimetal bearings including low cost, good wear resistance, and excellent corrosion resistance. Among bimetal bearings, the earliest examples utilized a lining alloy of AlSn20Cu1. This alloy had the advantage of very good conformability with misaligned shafts or shafts of poor geometric shape, due to its low hardness and high tin phase content. More advanced bimetal bearing alloys had increased strength and wear resistance due to higher hardness, addition of hard particles such as silicon, and decreased amount of tin. However these alloys suffer from a decrease in conformability compared to the AlSn20Cu1 alloy.
Several factors known in the art for improving the fatigue strength and performance of bearings include: (a) inclusion of a soft phase, such as tin or lead within the alloy layer to impart seizure resistance to the lining alloy; (b) inclusion of hard particles within the aluminum alloy such as silicon to increase the wear and seizure resistance of the alloy; (c) inclusion of an interlayer between the aluminum bearing alloy and the steel backing to achieve bonding between the lining and the steel when the amount of the soft phase exceeds about 10% by weight. However, there is little prior art regarding improving the conformability of the bearing, except for decreasing hardness and increasing soft phase content, both of which have a negative effect on the bearing lining fatigue resistance.
A sliding bearing constructed according to the invention has a steel backing on which a bi-metal lining is bonded. The lining includes an aluminum-based bearing layer and an intermediate layer of aluminum-based metal disposed between the bearing layer and the steel backing. The composite bearing material exhibits a high level of conformability while retaining good fatigue strength.
The invention has the advantage of providing a bi-metal aluminum bearing with a fatigue strength at a level normally associated with conformability normally associated with AlSn20Cu1 lined bearings.
The bearing material has the further advantage of providing an aluminum-based bearing layer that has a fine microstructure and lower tin content; thereby improving the fatigue strength of a bearing produced from the composite bearing material to a level normally associated with modern Alxe2x80x94Snxe2x80x94Si alloy lined bearings.
There is also disclosed a method of manufacturing a composite bearing including the steps of: a) casting an aluminum alloy to produce an aluminum-based bearing layer having silicon particles of less than 4 microns in average diameter dispersed uniformly therein, and a soft phase having a maximum length of 250 microns; b) cladding an aluminum-based intermediate layer material to said aluminum-based bearing layer to produce a bi-metal lining; and c) hot or cold bonding a steel backing layer to said bi-metal lining.